1. Field of the Invention
The invention relates to a seal for rotating shafts, especially for stern tube seal apparatus, using radial lip seals which bear in sealing manner against the shaft or a shaft bush.
2. Description of Prior Art
Seals are known, especially stern tube seals, in which a number of radial lip seals are arranged one after the other. After one or more of these sealing rings have worn out it is necessary to change the sealing rings. In order to permit of further running with the seal when a sealing ring has worn out it is known that one can provide a reserve slide ring or a reserve sleeve sealing ring which is brought into operation by a support device after the particular working sealing ring has worn out.
Furthermore a sealing arrangement for stern tube seal apparatus has been proposed which uses stationary sealing rings, such as bellows sleeves or the like, sealing against a bush rotating with the propeller shaft, which is provided on the sides facing the ship of the front and rear seal with spaces shaped like hollow rings for taking replacement seals, and where the spaces have a filling of coolant for the external cooling of the built-in active sealing rings and of the stern tube bearing, and at the same time hold replacement sealing rings; in this case the filling with coolant completely surrounds the replacement sealing rings. In the case of this seal, after a damaged lip seal has been destroyed and removed a reserve sealing ring is brought into the operating position by a support.
Finally a seal for stern tubes for ships is known in which a plurality of sealing rings are arranged at a distance from one another on a support, and in which one or more reserve sealing rings are provided. In this design, the support of the sealing rings can move axially relative to the shaft or bush and the diameter of the shaft or bush in the axial zone which is opposite the reserve sealing ring or the reserve sealing rings in the out-of-operation position is smaller than the internal diameter of the reserve sealing ring or rings, whereas in the axial zone in which the reserve sealing ring or rings are in the working position it is so great that the reserve sealing ring or rings bear in sealing manner on the shaft.
The problem underlying the invention consists in providing, in the case of seals of the above-mentioned type for rotating shafts using at least one sealing ring which can be moved into a working position, a simple and effective control for moving the reserve sealing ring support with at least one reserve sealing ring or also the operational sealing rings into a working position, in which this displacement movement of the reserve sealing ring or rings or also of the working sealing rings is achieved by using a pressure medium.